The present invention relates generally to blank printing plates mounted on cylindrical rollers or mounting tables, and more particularly, is directed to a method and apparatus for laser ablating an image on mounted blank printing plates.
It is known to provide an image on a printing plate, and thereafter, mount the printing plate on a roller for a printing operation. It is also known to mount a blank printing plate on a roller or mounting table for use in a printing apparatus, and thereafter, laser ablate the printing plate to produce an image on the mounted printing plate. The present invention is directed to the latter arrangement in which a blank printing plate is mounted, and then, the image is formed thereon.
It is well-known to use mounted blank printing plates in a printing operation. The printing rollers can include one or more sleeves and/or other layers thereon. The printing plates, after being mounted on the rollers, are etched or engraved in accordance with a desired image in order to effect the printing operation. It is also known to provide such etching or engraving of the image on the printing plate by means of a laser. An example of a system for performing this operation is disclosed, for example, in U.S. Pat. No. 7,284,484, which discloses the laser ablating of a blank printing plate mounted on a printing roller.
When laser ablating an image onto the printing plate, all areas which are not image transfer areas, including edges of the printing plate, are always laser ablated to form recesses or reliefs at which no printing occurs. Thus, the areas of the printing plate outside of the image area are laser ablated to provide recesses or reliefs, which do not affect printing.
However, a problem with this operation is that the laser will oftentimes extend past an edge of the printing plate during the laser ablating operation, and inadvertently and undesirably laser ablate a portion of the roller, the sleeve mounted on the roller or the mounting table, on which the printing plate is mounted. This, however, can damage the roller, the sleeve or the mounting table.
There are several ways to avoid damage to the roller, sleeve or mounting table, including but not limited to, masking the edges of the printing plate with a reflective foil, which reflects the laser and protects the roller, sleeve or mounting table from damage. It is also possible to provide a printing plate which has significantly larger size than the area of print needed, to ensure that the laser starts and stops within the boundaries of the printing plate. However all of these methods can require additional equipment, materials, time and expense, to make them work.